This application claims priority on Brazilian Patent Application, Serial Number 9805340-0, filed on Dec. 14, 1998, entitled VARIABLE EXPANSION INSERT FOR STABILIZING THE VERTEBRAL COLUMN, whose disclosure is incorporated by reference herein.
Numerous types of devices or systems are available for the fixation of the vertebral column of living beings. For example, some devices are prostheses, e.g., plates or other structures, formed of rigid materials of fixed sizes and volumes capable of being fastened, e.g., bolted, to the bony structure of vertebral column anteriorly and/or posteriorly through bores excavated in those vertebrae involved. The fasteners used in such devices or systems are commonly referred to as cortical bolts or medullary bolts, depending upon the type of thread of the bolt. In some systems or devices parts of human bone from the patient himself/herself, or from bone banks or dehydrated human bone is used to aid in securing the prosthesis to the bony structure(s) of the vertebrae. One of the greatest drawbacks of such prior art devices or systems are that they are difficult to use. In this regard, the deployment and mounting of a bolt-based fixation device is delayed by the necessity to bore the bony structures of the vertebrae for receipt of the securement bolts. Moreover, the location of the bore holes for those bolts must be precisely located and oriented to match up with the pre-established holes in the plates or other support structures forming the remainder of the device or system. Another drawback of such spine fixation devices is the fact that they typically take up such substantial space in the body when secured in place, that they may result in the formation of traumatic lesions to adjacent anatomic structures. Lastly, traction exerted by movement of the patient, may cause partial or total detachment of one or more of the bone fixation bolts, which action may also result in the formation of traumatic lesions to adjacent anatomic structures and/or instability of part or all of the fixation system.
Various patents and printed patent literature have also disclosed devices and systems for fixation or stabilization of the spine or vertebral column of a living being. See for example, U.S. Pat. No.: 4,863,476 (Shepperd), U.S. Pat. No. 5,591,235 (EKuslich), U.S. Pat. No. 5,653,761 (Pisharodi), U.S. Pat. No. 5,653,762 (Pisharodi), U.S. Pat. No. 5,653,763 (Errico et al.), U.S. Pat. No. 5,693,100 (Pisharodi), U.S. Pat. No. 5,713,904 (Errico et al.), U.S. Pat. No. 5,782,832 (Larsen et al.), U.S. Pat. No. 5,865,847 (Kohrs et al.) and U.S. Pat. No. 5,865,848 (Baker), PCT Application Publication Nos.: WO 90/00037, WO 95/31158, WO 97/06753, and WO 98/10722, European Patent Application Nos.: 0 599 766 A1, and 0 635 246 A1, Spanish Patent No. ES 2 099 008, and Russian Patent No.: 2063730.
While the spine stabilization or fixation devices of the patent literature may be generally suitable for their intended purposes, they still leave much to be desired from the standpoints of ease of use and effectiveness. For example, some prior art spine fixation devices require excision of the anterior and/or posterior ligaments, thereby destabilizing the spine. Thus, these systems require some mechanical means to fuse or fix the adjacent vertebrae to each other, e.g., removal or drilling of the bone to secure the device in position with respect to each vertebra with some type of mechanical bridge therebetween. Other types of fixation devices make use of hollow or apertured implants designed to be packed with bone chips or particles and placed into excavations through the exterior, hard cortical bone, into the soft interior cancellous bone of opposed vertebrae to facilitate the ingrowth of bone into the implant and thus fuse the two vertebrae together. This type of fixation device may be prone to damage the immediately adjacent vertebrae due to compressive forces thereon.
While some prior art devices don't require excision of the ligaments to effect spine stabilization, they, nevertheless, typically require the partial or complete extraction and removal of the disk in order to place them into the intervertebral space, where such devices seek to replace the function of the disk (albeit less than optimally).
Notwithstanding all of the prior art now in existence, a need still exists for a spine stabilization system which is easy to use, effective, and safe.